The present invention relates to an information processing apparatus, authentication processing method, and computer program. The present invention further relates specifically to an information processing apparatus, authentication processing method and computer program for preventing illegal use of content.
In recent years, discs capable of storing large volumes of data such as DVDs and blue-laser discs (Blu-ray Disc, a trademark) have been utilized and developed that are capable of saving and playing large volumes of data such as high-definition images and high-quality audio. Further, development and utilization not just of conventional consumer recording/playback devices but also of personal computers installed with high-performance CPUs and video cards and other information playback devices as playback environments for these large capacity recording media is also taking place.
For example, a problem with playing back content on a PC is providing copyright protection for content. Distribution rights for a large amount of content such as music data or image data and the like are typically retained by the author or seller. Typically, a configuration is adopted where fixed utilization limits are adopted while distributing content, i.e. only proper users are allowed to utilize content so as to ensure that illegitimate duplication and the like is not carried out.
In particular, according to digital recording devices and recording media, it is possible to repeatedly record and playback without deterioration of images and audio. This brings about the problem of the distribution of illegally copied content via the Internet and the dissemination of pirated discs where content of recording media such as CD-Rs and DVDs and the like is copied.
Various image information and music information that is the subject of copyright protection is put on the marketplace stored as digital data on a large capacity type recording medium such as a DVD or blue laser disc and the like. A configuration that prevents illegal copying to protect copyrights is therefore necessary when media recorded with digital data are put on the marketplace. Recently, various technologies for preventing unlawful copying have been implemented at digital recording devices and recording media in order to prevent this kind of illegal copying of data.
For example, DVD players adopt a content scrambling system (CSS: content scrambling system). With content scrambling systems, video data and audio data and the like is recorded on a recording medium such as, for example, a DVD-ROM (Read Only Memory). A key used in decryption of this encrypted data is then only provided to players that have received a license. A license is only provided to players designed according to prescribed operation regulations such as illegal copying is not to be carried out, and the like. Players that have received a license are then capable of playing back images and audio by utilizing a provided key to decode encrypted data recorded on an information recording medium.
On the other hand, players that do not have a license do not have a key for decrypting encrypted data and therefore cannot decrypt the encrypted data recorded on the information recording medium. A content scrambling system (CSS) therefore provides a system that grants utilization of content only to players having the proper license.
However, this content scrambling system (CSS) is not capable of eliminating illegal utilization of content in a reliable manner. In particular, problems occur where illegal utilization of content may be carried out in processing for outputting and playing back content from a drive installed with an information recording medium at an information processing apparatus such as a PC and the like. A description is given of these problems with reference to the drawings.
An example of stored data of an information recording medium for storing content adopted in a content scrambling system (CSS) and processing of playback equipment (player) is shown in FIG. 1.
An information recording medium 10 shown in FIG. 1 is, for example, a DVD video disc. A secured disc key 11, secured title key 12 corresponding to the title of the content stored on the information recording medium 10, and scrambled MPEG data 13 taken as content subjected to scramble processing based on a CSS method are stored in the information recording medium 10.
Playback equipment 20 in which the information recording medium 10 is installed, for playing back and executing content, such as, for example, a DVD player applies a master key stored in the playback equipment 20. In step S11, decryption processing is performed using a secured disc key 11 acquired from the information recording medium 10 and a disc key is acquired. In step S12, the acquired disc key is applied in the execution of decryption processing of a secured title key 12 acquired from the information recording medium 10. The acquired title key is then applied in step S13 so that, after executing de-scrambling processing of the scrambled MPEG data 13, in step S14, MPEG decode processing is executed, and audio/visual data 25 is played back.
Next, a description is given with reference to FIG. 2 of a processing sequence for inputting content of a drive provided at or connected to a host device such as a PC and the like to the host (PC) side and playing back the content using a player application on the host-side.
As shown in FIG. 2, in step S31 and S41 shown in FIG. 2, authentication and key exchange takes place between a drive 30 in which the information recording medium is installed and a host (PC) side player application 40. The authentication processing is executed in accordance with an algorithm such as, for example, a public key encryption method or a shared key encryption method. A session key is generated in the authentication and is shared by the drive 30 and the host-side player application 40.
In step S32, the drive 30 applies the session key so as to re-encrypt the secured disc key 11 acquired from the information recording medium 10 and send this to the player application 40. Further, in step S33, the drive 30 applies the session key so as to re-encrypt the secured title key 12 acquired from the information recording medium and send this to the player application 40. A PC constituting an execution device for the drive 30 and the player application 40 is connected by a connection bus such as, for example, an API bus (AT Attachment with Packet Interface BUS) and sends the secured key information to the side of the player application 40 of the PC via the connection bus.
The drive 30 then outputs scrambled MPEG data 13 constituting content acquired from the information recording medium and subjected to scramble processing based on the CSS method to the side of the PC via the connection bus between the drive and the PC.
In step S42, the host (PC) side player application 40 decrypts the data re-encrypted using the session key of the secured disc key 11 received from the drive 30 using the session key. Further, in step S43, the host (PC) side player application 40 decrypts the re-encrypted data using the session key of the secured title key 12 and acquires the secured title key 12.
Subsequent processing of step S51 to S55 is then similar to processing (S11 to S14) already described with reference to FIG. 1.
A flowchart of a process on the drive-side occurring in the processing in FIG. 2 is shown in FIG. 3. When it is determined, in step S61, that an information recording medium (disc) is inserted, in step S62, authentication and key exchange is executed with the host, i.e., with the PC executing the player application 40 shown in FIG. 2.
When the authentication and key exchange is successful (step S63: Yes), a transition is made to a state where output of CSS scramble data constituting content stored on the information recording medium installed in the drive is permitted. The state where output of the CSS scramble data is permitted continues until the information recording medium is ejected or until a power supply is turned off.
In the event that content in a host device such as a PC or a connected drive is inputted to the host (PC) side and content is played back by a host-side player application, authentication is carried out between the host-side player application and the drive so that data is transferred in a secure manner. Authentication can therefore be performed between the host-side player application and the drive so that data is transferred in a secure manner while recording data on the information recording medium (disc).
However, authentication processing is executed as processing conforming to a specific sequence and authentication is established by fulfilling prescribed conditions. For example, in an authentication algorithm conforming to a public key method, authentication is established for equipment executing authentication as a result of a condition of having a key pair of a public key that in itself is ineffective and a private key being fulfilled.
A public key is stored in a public key certificate issued by a prescribed management center and is affixed with an electronic signature of the management center, which makes falsification difficult. Further, in the event that illegal processing such as the dissemination of illegally copied keys occurs, processing is carried out where a public key certificate for issuance completion is invalidated (revoked) under the management of the management center. In this invalidation (revoking) processing, a management center issues a revoke list (CRL: Certificate Revocation List) listing identifiers (IDs) of invalidated public key certificates.
Equipment executing authentication in accordance with public key encryption methods obtains newly updated revoke lists via a network or recording medium and the like. Revoke lists obtained in this manner are then referred to when executing authentication processing and validity of public key equipment of other equipment being authenticated is determined. In the event that an ID of a public key certificate for an opposing item of equipment is recorded on the revoke list, this is determined to be an illegal public key certificate, and authentication therefore fails.
However, there is a problem that there is a considerable amount of time until exclusion of utilization of illegal key information based on the revoke list, and during this time illegal utilization of content is difficult to prevent. For example, after processing of illegally utilized public keys and secret keys due to disclosure of a public key and private key and the like, the illegal processing is authenticated by the management center. Processing for recording to the revoke list then takes place and distribution of the updated revoke list to each device begins. Exclusion of illegal keys using the updated revoke list is then possible in subsequent authentication processing.
Cases where a number of months are required until this processing is complete are common. If verification of the disclosure by the management center does not take place, the illegal dissemination of key information remains as it is.
As a result, with this configuration where content is utilized taking the establishment of authentication between a drive and a host application as a condition, in the event that an illegally obtained key pair of a public key authentication certificate and a secret key is present at either one of the drive or the host application so that verification of illegality using the revoke list is not possible in the authentication processing, authentication is established, and content may be illegally obtained and utilized by the drive or host application in possession of the illegal keys.
A specific example of this is described with reference to FIG. 4 and FIG. 5. FIG. 4 is a view showing processing where authentication is executed based on a public key encryption algorithm between a drive 60 and a host-side player application 70, and content is read from an information recording medium 50 installed in the drive 60 taking establishment of authentication as a condition, then played back and utilized.
It is taken that the host-side player application 70 is in possession of illegal keys 71 including an illegally obtained public key PH and private key SH. The public key PH is stored in the public key certificate. However, this is not yet recorded in the revoke list issued by the management center, and exclusion based on the revoke list is not possible.
In this state, authentication and key exchange processing (Step S81) is executed between the drive 60 and the host-side player application 70 based on a public key encryption algorithm. Authentication and key exchange processing (AKE) is processing sharing authentication processing and a session key (Ks). The session key (ks) may be utilized in public key encryption during data communication executed between authenticated equipment.
In the authentication and key exchange processing of step S81, both the drive 60 and the host-side player application 70 exchange public key certificates stored in public keys, signature authentication of the public key certificates and revoke verification based on the revoke list are carried out and propriety is confirmed.
When the public key certificate signature received from the player application 70 is authenticated, the drive 60 carries out revoke verification based on the revoke list and propriety is confirmed. The public key for the player application 70 is an illegal key but at this point in time this illegal key is not recorded in the revoke list. The drive 60 therefore determines the public key to be trustworthy and authentication is established.
After this, in step S82 and step S83, the drive 60 encrypts encrypted content read out from the information recording medium 50 and a content key (Kc) constituting a secure key for encrypted content using a session key (Ks) and outputs this to the player application 70.
In step S84 and step S85, the player application 70 applies the session key (Ks) so as to decrypt data received from the drive 60, acquires encrypted content and the content key (Kc), and in step S86, applies the content key (Kc) to decrypt encrypted content and acquire the content.
This means that even if a key is acquired illegally, it is not known that the key is illegal while the key is not recorded on the revoke list. Authentication is therefore established, and content subject to copyright management and utilization management stored in the information recording medium 50 can therefore be illegally read out and utilized by an illegal application.
FIG. 5 shows an example of illegal utilization of content in the case where the side of the drive 60 is in possession of illegal key information [SD, PD].
In the authentication and key exchange processing of step S91, both the drive 60 and the host-side player application 70 exchange public key certificates stored in public keys, signature authentication of the public key certificates and revoke verification based on the revoke list are carried out and propriety is confirmed. When the public key certificate signature received from the drive 60 is authenticated, the player application 70 carries out revoke verification based on the revoke list and propriety is confirmed. The public key for the drive 60 is an illegal key but at this point in time this illegal key is not recorded in the revoke list. The player application 70 therefore determines the public key to be trustworthy and authentication is established.
After this, in step S92, the player application 70 applies a content key (Kc) obtained through a normal procedure so as to encrypt content acquired through a normal procedure from, for example, a network. Next, in step S93 and step S94, the encrypted content and the content key (Kc) constituting a secure key for encrypted content are encrypted using a session key (Ks) and outputted to the drive 60.
In step S95 and step S96, the drive 60 applies the session key (Ks) to decrypt data received from the player application and acquires encrypted content and the content key (Kc). In step S97, decryption of encrypted content is executed by applying the content key (Kc) so as to acquire content, and this content is recorded on a recording medium such as, for example, a CD-R and the like.
In this way, even if a key is obtained illegally, it is not known that the key is illegal while this is not recorded in the request list. It is therefore possible for content obtained from outside by a player application 70 using a normal procedure to be obtained by an illegal drive so as to make it possible to create an illegal content recording medium such as a CD-R and the like.
This means that the current situation is that it is difficult to completely prevent illegal utilization of content by only using a configuration for excluding illegal keys that is only based on a current revoke list.